1. Field of the Invention
The invention is directed to a method for the encryption of information for a radio transmission and for authentication of subscribers in a communication system and is also directed to a corresponding communication system.
2. Description of the Related Art
Communication systems such as the mobile radio telephone system according to the GSM standard (global system for mobile communication) use a radio interface for wireless information transmission. Connections between mobile stations and base stations of a mobile radio telephone network can be setup, released and maintained on this radio interface. A method and a system for encryption (ciphering) information for radio transmission and for subscriber authentication are known from the article “Safety First bei europaweiter Mobilkommunikation” telcom report 16 (1993), No. 6, pages 326 through 329. In this article, the mobile subscribers identify themselves with respect to the mobile radio telephone network using a subscriber identity mobile (SIM)card/that is contained in the radio telephone subscriber station. At the network side, the mobile subscriber is registered in a an authentication means (authentication center)/that respectively offers security parameters and security algorithms for the protection of the subscriber data of the mobile subscribers. The encryption of the information on the radio interface takes place in a subscriber-related manner and is directly coupled to the subscriber authentication.
In future communication systems, such as a universal network (UMTS, universal mobile telecommunication system or UPT, universal personal communication), there is a tendency to divide the infrastructure into an access network and into one or more core networks. The area of the access network in these system's responsible for matters of the radio interface such as administration and allocation of the radio channels, channel encoding, encryption via the radio interface. By contrast, the area of the core network is mainly responsible for matters of the subscriber administration such as registration (subscription), authentication, selection of the access network, etc., as well as for offering services. An encryption of the information for the radio transmission independently of the core network is impossible in the current GSM system. Over and above this, a radio resource, for example the radio channel, is exclusively used for only one subscriber in the encryption, namely the subscriber that was authenticated at the moment. This is no longer adequate for future communication systems, particularly given a simultaneous use of a mobile station by a plurality of subscribers (for example, with their SIM cards).